Valve seat drop damage = complete engine destruction. We've seen these where the valve seat drops, engine won't start, combustion chamber and that piston are scarred and slightly damaged. Then we've seen where the valve seat drops, the piston has a hole on it, the head is cracked, and there is a hole in the cylinder wall. It's hard to say how it will happen.
Yes, new valve seats can fix it forever, but unless there is a reason to disassemble the engine- like a new head gasket is needed, or a timing belt must be replaced- then I don't see as you should bother with it. Yes, there's a chance it will KO everything, but I don't see at 120k miles that there's a point to it unless you're experiencing some of the problems associated with imminent valve seat drop. You might want to purchase a compression tester, it's not an expensive tool, and then do periodic compression tests to see if you have a valve seat problem.
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Originally Posted by the user formerly known as ZX3_Chick
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